Five Whys

Joel Spolsky on uptime guarantees:

Really high availability becomes extremely costly. The proverbial “six nines” availability (99.9999% uptime) means no more than 30 seconds downtime per year. That’s really kind of ridiculous. […] Think of it this way: If your six nines system goes down mysteriously just once and it takes you an hour to figure out the cause and fix it, well, you’ve just blown your downtime budget for the next century.

★ Tuesday, 29 January 2008